Tailoring of rheological properties and structural polydispersity effects in microfibrillated cellulose suspensions
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ORIGINAL RESEARCH
Tailoring of rheological properties and structural polydispersity effects in microfibrillated cellulose suspensions Goksu Cinar Ciftci Hans Henrik Øvrebø
. Per A. Larsson . Anastasia V. Riazanova . Lars Wa˚gberg . Lars A. Berglund
.
Received: 28 April 2020 / Accepted: 3 September 2020 Ó The Author(s) 2020
Abstract Industrial production of low-charge microfibrillated cellulose (MFC) typically results in wide fibril size distributions. This polydispersity influences viscosity, overall colloidal stability, and rheological properties of MFC suspensions and gels in aqueous systems. In this work, a systematic rheological analysis is performed for industrially prepared MFC and fractions of different size distributions. Gel formation and flow characteristics (e.g., shear-thinning) of each fraction are examined under neutral and acidic conditions and compared with the unfractionated MFC suspension. The effects of size, aspect ratio, and surface charge on the rheology of semi-dilute MFC suspensions are discussed. The results
demonstrate that particle size and aspect ratio distribution control the viscoelasticity and shear-thinning properties of MFC suspensions. An increased fraction of small diameter nanofibrils, by ex situ addition of the fine particles with high aspect ratio or removal of the coarsest particles (with lower aspect ratio) by fractionation, significantly enhances the storage modulus and the yield stress of the complex mixture, compared to the properties of the coarser fractions. New insights are also reported on the tailoring of the rheology of highly polydisperse fibrillar mixtures, where the rheological contributions of each fraction are discussed.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10570-020-03438-6) contains supplementary material, which is available to authorized users. G. Cinar Ciftci (&) P. A. Larsson A. V. Riazanova L. Wa˚gberg L. A. Berglund Department of Fibre and Polymer Technology, KTH Royal Institute of Technology, Stockholm, Sweden e-mail: [email protected] H. H. Øvrebø Borregaard AS, Sarpsborg, Norway
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Cellulose
Graphic abstract
Keywords Nanocellulose Cellulose nanofibrils Viscoelasticity Gel formation Shear-thinning
Introduction Plants are sustainable sources of advanced materials, with the ability to provide us greener alternatives to today’s commercially available petrochemical-based products. Cellulosic materials with their exceptional physical and mechanical properties have been used for textiles, construction materials, and papermaking for centuries (Hon 1994). The disintegration of cellulose fibres, with different combinations of pre- and posttreatment, has led to the development of cellulose nanomaterials, such as cellulose nanofibrils (CNF; also called nanofibrillated cellulose, NFC) and microfibrillated cellulose (MFC). These cellulose nanomaterials have a large specific surface area, semi-crystalline order, and a variety of function
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